you need to do some reading about bikes on the back bumpers of TT's, because it's not generally advised, ESPECIALLY a 4-bike rack system.
does your Salem have a factory installed receiver?
if not, installing one on the bumper or welding it on the frame, will void the frame's warranty unless it's already expired.
search any RV forum on bike racks on rear bumpers and see for yourself.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC